Archaeologists digging in Pompeii have unearthed a rare fresco depicting the mythological sexual encounter between the Spartan queen Leda and the god Zeus in the form of a swan. The wall painting adds to the already rich catalogue of erotica found among the ruins of the ancient Roman city.

The fresco, whose discovery was announced Monday, emerged on the wall of a lavish Roman house that had become blanketed in ash and debris along with the rest of Pompeii and nearby settlements when Mt. Vesuvius erupted in 79 C.E.

The explicit painting shows a semi-naked Leda sensually draped over a chair with the swan sitting in her lap while nuzzling her neck. The woman’s eyes are painted to look straight at the observer, as if catching any onlookers in a voyeuristic act.

Erotic art is legion in Pompeii, and depictions of people having sex (sometimes with animals) and/or men sporting enormous phalluses abound. In the summer, archaeologists digging in the same villa where the Leda fresco was found uncovered an image, decorating the building’s entrance, of the god Priapus weighing his penis, a fairly common motif in the city.

Still, the new find is “exceptional and unique for its decisively sensual iconography,” says Massimo Osanna, the director of the Pompeii Archaeological Park.

The image is very different from other more common portrayals of the story that were found in Pompeii and elsewhere, which don’t often depict the sexual act and tend to show Leda standing while being pursued by the swan, Osanna said.